Roll src/third_party/webrtc b571ff48f8fe..2288256c9a7a (3 commits)

https://webrtc.googlesource.com/src.git/+log/b571ff48f8fe..2288256c9a7a

git log b571ff48f8fe..2288256c9a7a --date=short --first-parent --format='%ad %ae %s'
2020-04-06 kthelgason@webrtc.org Add ObjC Interface for VideoEncoderSelector.
2020-04-06 danilchap@webrtc.org Drop support of sending generic frame descriptor v1
2020-04-06 chromium-webrtc-autoroll@webrtc-ci.iam.gserviceaccount.com Roll chromium_revision f099852e..15f45a68 (756498:756615)

Created with:
  gclient setdep -r src/third_party/webrtc@2288256c9a7a

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/webrtc-chromium-autoroll
Please CC webrtc-chromium-sheriffs-robots@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

Bug: None
Tbr: webrtc-chromium-sheriffs-robots@google.com
Change-Id: I43454788a37d6681ccdd1e9c14dc9f0eeda05bb7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2136460Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#756705}

DEPS

@@ -1458,7 +1458,7 @@ deps = {
   },
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + 'b571ff48f8fe07678da5a854cd6c3f5dde02855f',
+    Var('webrtc_git') + '/src.git' + '@' + '2288256c9a7a5a23507e0662fb03d95c86f04368',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),